Complex shaped 3D objects fabrication

ABSTRACT

A method employs a first polymeric material to deposit first and second pattern layers laterally shifted from each other such that laterally shifted pattern layers form between them an empty volume with a variable cross-section that varies along with the first and second pattern layers. A second polymeric material is cast in the empty volume between the first and second pattern layers to cast a complex-shaped 3D object identical in shape to the empty volume between the first and second pattern layers. Radiation is applied to cure the first and second polymeric materials. The first polymeric material is a water breakable material composition including acrylamide, methacrylamide, acrylate, acrylic acids, and acrylic acid salts, hydroxy(meth)acrylate, carboxy(meth)acrylate, acrylonitrile, carbohydrate monomers, methacrylate and polyfunctional acrylics.

This application is a continuation of U.S. application Ser. No.16/351,599, filed on Mar. 13, 2019, which is a division of U.S.application Ser. No. 15/960,584, filed on Apr. 4, 2018, now U.S. Pat.No. 10,328,635, issued on Jun. 25, 2019, which claims the benefit ofU.S. Provisional Patent Application 62/595,096, filed on Dec. 6, 2017,which is incorporated herein by reference.

TECHNOLOGY FIELD

The present method and apparatus relate generally to manufacturing of 3Dobjects. More particularly, the present method and apparatus relate toautomated methods and equipment for complex shaped 3D objectsmanufacture.

BACKGROUND

Three dimensional printing is a generic term encompassing differentadditive manufacturing technologies such as inkjet printing, selectivematerial deposition, material extrusion, material sintering and others.The object is produced by depositing a layer of a material on top orbottom of previously deposited or dispersed layer of material andbecause of this is termed additive manufacturing (AM) process. In alarge majority of cases the material from which the object is producedis a polymer that adheres to the previously deposited layer and ishardened or solidified by actinic radiation, such as ultravioletradiation, thermal sources and others.

Most objects are not simple in their structure and include segments ofcomplex shapes such as curved surfaces and surfaces that could overhangoutside the main body of the object or in case a hollow object, protrudeinto a hollow void or cavity inside the object defined by the objectwalls. The surfaces could be inclined, oriented at different angles andhave different thicknesses or sizes. Different types of material layershaving different properties and strength could be required to print suchobjects. Composite materials are among the strongest materials used inmanufacture of different objects. Composite materials offer unusualselection of properties while additive manufacturing processes providesome advantages for fabrication of objects with complex shapes.

Some composite materials are manufactured by forming the object bydeposition of a mix of components that include for example, fibers mixedwith different resins. Mixes of metal and metal matrices, glass,ceramics and ceramic matrices elements with resins are also known. Thecarbon, glass or aramid reinforcements usually are supplied in the formof a fabric. The process is largely manual, although machines for layingdown different material fabrics and spraying over them a resin exist. Asandwich structured composite is a special class of composite materialthat is fabricated by attaching two thin but stiff skins to alightweight and thick core. The skins are the outer layers and areconstructed out of a variety of materials. Wood, aluminium, and plasticsare commonly used. More recently though, advanced fiber reinforcedcomposites are being used as skin materials. The manufacture of such 3Dpanels is relatively a straightforward process, however manufacture ofcomplex 3D shapes is more challenging.

Complex, three-dimensional shapes are used in building boats and shipswhere decks and hulls are commonly made with curved composite laminatesor sandwich type structures. Ships utilize curved composite laminatesand sandwich type materials to reduce ship weight. In aerospace, complexthree-dimensional shapes have been used for wings, doors, controlsurfaces, tail planes, stabilizers for both military and civilaircrafts, vehicles, caravans, industrial machinery covers and otherarticles.

A plurality of complex objects or articles such as impellers, rotor andengine blades, and a variety of other objects could also be manufacturedusing 3D printing techniques. Generally, an infinite variety of articlesand complex objects can be manufactured using 3D printing, Production ofsuch complex objects requires production of special large size mouldsthat by itself is a complicate labour-intensive task.

Although the number of materials currently used in 3D objectsmanufacture is not large, it is suitable for manufacture of a largeselection of 3D objects. The color of the available materials issomewhat limited and the size of the 3D objects produced by the existingequipment is also limited. Usually, large size products are manufacturedin several pieces that must be assembled into a finished product, whichcould be a challenging task.

Printing of three-dimensional articles is described in several UnitedStates patents, including the following U.S. Pat. No. 5,204,055 to Sachset al., U.S. Pat. No. 6,193,923 to Leyden, U.S. Pat. No. 6,397,992 toSachs et al., U.S. Pat. No. 6,627,835 to Chung, U.S. Pat. No. 7,074,358to Gybin, U.S. Pat. No. 8,309,229 to Nakahara, U.S. Pat. No. 8,974,213to Yakubov, U.S. Pat. No. 9,162,391 to Yakubov, U.S. Pat. No. 9,216,543to Lisitsin, U.S. Pat. No. 9,623,607 to Uzan, US Pat. Appl. Pub. No.20030085383 to Burnell-Jones, US Pat. Appl. Pub. No. 20040198861 toOhno, US Pat. Applic. Pub. No. 20070181519 to Khoshnevis, US Pat. Appl.Pub. No. 20110166056 to Huber, US Pat. Appl. Pub. No. 20150321385 toStege.

Definitions

As used in the current disclosure the term “complex shaped 3D object”means a 3D physical object including curved surfaces that could beconvex or concave, flat surfaces and surfaces that could overhangoutside the main body of the object or in case a hollow object, protrudeinto a hollow void or cavity inside the object defined by the objectwalls. The surfaces could be inclined, oriented at different angles andhave different thicknesses or sizes. Complex shaped 3D objects could bemade of any type of homogeneous or composite material.

As used in the current disclosure, the term pattern layer/s meanselements that when deposited on a substrate or printing apparatus tableform an empty space into which an additional material could be depositedor casted.

The term Dalton is a System International (SI) unit for molar mass andbecause of historical reasons it is also used to designate molecularweight.

SUMMARY

A method and apparatus for manufacturing of 3D objects. The apparatusincludes a number of material deposition heads terminated by nozzles, ofwhich one or two nozzles are configured to deposit a first material toform a first and second pattern layers. The pattern layers are laterallyshifted from each other such that when the first and second patternlayers are deposited, a space (empty volume) with a cross section thatvaries between the first and second pattern layers is formed. In someexamples, only one nozzle could be used to deposit the first and secondpattern layers. In other examples, two or more nozzles could be used todeposit the corresponding first and second pattern layers. The nozzlescould move independently of each other.

An additional material deposition nozzle is configured to deposit in thespace between the first and second pattern layers a second material. Thesecond material fills the space between the first and second patternlayers and forms a complex shaped 3D object identical in shape to thespace between the first and second pattern layers. In some examples themethod and apparatus are characterized in that the first and secondpattern layers and the complex shaped 3D object are depositedsequentially, although in some examples the first and second materialcould be deposited simultaneously or almost simultaneously.

Typically, the materials from which the first and second pattern layersand the second material are materials that when exposed to actinicradiation, temperature or pressure, or mixture of resin and hardener,change their aggregate state, i.e, the materials are solidify or harden.Accordingly, both materials change their aggregate state. Typically, thepattern layers solidify before the second material is deposited. Thefirst material has mechanical properties different from the secondmaterial. The second material supports inclusion into it of additionalmaterials or additives. The additional materials or additives could haveproperties different from the properties of the second material, forexample, ceramic, metal or mineral powder fillers, glass and otherfibres, rheological modifiers and other materials. The additionalmaterials could enhance a desired property of the second material.

Upon completion of the second material hardening, the pattern layers areremoved by any known removal method and in particular by exposure to tapwater, heat or mechanical action. The patterning layers display highwater absorption, but limited swelling, therefore, the pattern materialbreaks into beads, followed by washing it with excess of water. Thepattern layers material composition is based on hydrophilic monomerscombined with hydrophilic or hydrophobic cross linkers. This chemicalstructure allows rapid swelling of the polymer but not fully dissolve inthe water. The outcome of high stress, the hydrogel break into beadsthat can be easily collected into a mesh, for example, by filtering thewater through a mesh filter.

In one example the material deposition nozzles and the table havefreedom of linear movement with respect to each other in three differentdirections. In an additional example, the material deposition nozzlesare configured to move in a radial and axial directions and the table isconfigured to rotate and move in a desired direction.

A method of an embodiment employs a first polymeric material to depositfirst and second pattern layers laterally shifted from each other suchthat laterally shifted pattern layers form between them an empty volumewith a variable cross-section that varies along with the first andsecond pattern layers. A second polymeric material is cast in the emptyvolume between the first and second pattern layers to cast acomplex-shaped 3D object identical in shape to the empty volume betweenthe first and second pattern layers. Radiation is applied to cure thefirst and second polymeric materials. The first polymeric material is awater breakable material composition including acrylamide,methacrylamide, acrylate, acrylic acids, and acrylic acid salts,hydroxy(meth)acrylate, carboxy(meth)acrylate, acrylonitrile,carbohydrate monomers, methacrylate and polyfunctional acrylics.

LIST OF DRAWINGS AND THEIR BRIEF DESCRIPTION

The features and advantages of the disclosure will occur to thoseskilled in the art from the following description and the accompanyingdrawings, in which like parts have been given like numbers.

FIG. 1 is an example of a large size complex shaped 3D object;

FIG. 2 is another example of a large size complex shaped 3D object;

FIG. 3A is an example of an apparatus suitable for manufacture ofcomplex shaped 3D objects;

FIG. 3B is another example of an apparatus suitable for manufacture ofcomplex shaped 3D objects;

FIG. 4A is still another example of an apparatus suitable formanufacture of a complex shaped 3D objects;

FIG. 4B is still another example of an apparatus suitable formanufacture of a complex shaped 3D objects;

FIG. 5 is an example of pattern layers suitable for manufacture of heavycomplex shaped 3D objects;

FIG. 6 is a plan view of large size complex shaped 3D object;

FIG. 7A is a further example of a method of manufacture of a complexshaped 3D object; and

FIG. 7B is still a further example of a method of manufacture of acomplex shaped 3D object.

DESCRIPTION

Existing methods and apparatuses for fabrication of complex shaped 3Dobjects, such as large shells, moulds and similar are largely timeconsuming and labour intensive.

Typically, such complex 3D objects and in particular large complexshaped 3D objects are manufactured in several steps; first the complexshaped 3D object data is cut into segments, then each segment ismanufactured, and finally the segments are assembled into a largecomplex shaped 3D object. For example, a casting form, sometimes termedas a mould, is typically prepared from two or more separate segments orparts that are assembled into a final casting form. Then anothermaterial, from which the desired complex shaped 3D object will bemanufactured is deposited or casted into the earlier prepared castingform. These are time consuming and costly procedures.

The present disclosure describes a method and apparatus supportingfabrication of a complex shaped 3D object by depositing a pattern oflayer/s followed by filling the pattern with casting material. Themethod and apparatus facilitate production of casting forms and othertools necessary to manufacture complex shaped 3D objects.

The present disclosure also provides a manufacturing method of complexshaped 3D objects, which overcomes the disadvantages of the existingmethods, and provides a useful alternative for manufacture of largecomplex shaped 3D objects. The method suggests a sequential or almostconcurrent manufacture steps of the pattern layers and the complexshaped 3D object. Typically, the first and second pattern layers and thelarge complex shaped 3D object are manufactured in sequence where thefirst and second pattern layers are deposited first and following thepattern layers hardening, the large complex shaped 3D object material isdeposited.

Traditionally, manufacture of such complex shaped 3D objects orstructures is usually accomplished by introduction of so called supportelements or structures similar to scaffolds used in buildingconstruction. Upon completion of object manufacture, the supportelements have to be removed. In most cases the support structures areremoved by mechanical means such as knives, pliers and putty typescrappers. Use of such mechanical means requires significant manual workand subsequent processing to smoothen the surface where the support wasattached. Additionally, some support structures located in the innercavities of the mould or casted article cannot be removed.

Pattern layers usually have to meet a number of conditions: maintain theprinted object integrity, to be easily removable from the external andthe internal surface of the complex shaped 3D object and when removedthey do not damage the outer or inner surface of the complex shaped 3Dobject. In some examples, of the present disclosure the pattern layerscould be made of a tap water breakable material. Some pattern layersstructures could be easy breakable by heating or a mechanical force,such as hammering or pressure.

There is a need to simplify and accelerate production of tools forcomplex mould and casting forms production, using improved patternmaterials for 3D printing or extrusion, including pattern layersmaterials that can be strong enough and could be removed in an easy way.

FIG. 1 is an example of a large size complex shaped 3D object. Complexshaped 3D object 100 could be about 1500 mm or more high/tall and have adiameter of 400 or 500 mm. The object includes flat 104, convex andconcave surfaces 108. Additionally, the surfaces could be inclined,oriented at different angles and the walls of 3D object 100 could havedifferent thicknesses or sizes.

FIG. 2 is an example of another large size complex shaped 3D object.Complex shaped 3D object 200 could be a panel of a ship or a segment ofa plane. 3D Object 200 could be about 1500 mm long and have a thicknessof for example, 10 to 500 mm. The material of the complex shaped 3Dobject 200 is casted into a space between two stiff pattern layers 204and 208 and forms a core 212 located between pattern layers 204 and 208.Upon completion of core 212 hardening, pattern layers 204 and 208 couldbe removed. In some examples, pattern layers 204 and 208 could becombined with a bottom pattern layer 216 made of the same material aspattern layers 204 and 208 are made.

Complex shaped 3D object 200 is produced as a layered object. Byperforming several successive passes a desired number of hardenedpattern layers 220 of the first material could be deposited. In asimilar or different manner the casted complex shaped 3D object materiallayers 224 could be deposited and a complex shaped 3D object could bemanufactured or fabricated. Pattern layers 220 and casted objectmaterial layers 224 could be of the same or different thickness.Typically, casted complex shaped 3D object material layers 224 aredeposited after several pattern layers 220 are deposited and hardened.The delay could be defined by time required to deposit 3-30 patternlayers 220.

FIG. 3A is an example of an apparatus suitable for manufacture of acomplex shaped 3D object. Apparatus 300 includes a pattern layersmaterial deposition nozzle 304 configured to deposit a first or patternlayers material and a nozzle 312 configured to deposit a second orcasted article 340 material. The material deposition nozzle 304 isconfigured to deposit a first material to form a first 332 and second336 pattern layers. Since, the first 332 and second 336 pattern layersare laterally shifted, nozzle 304 could deposit them in differentmanners, e.g., build-up a certain height of pattern layer 332 and shiftto build-up a similar or different height of pattern layer 336. Thelaterally shifted first 332 and second 336 pattern layers form a space(empty volume) with a cross section that varies along the first 332 andsecond 336 pattern layers. Processor 330 is configured to receive thecomplex shaped 3D object data and convert it to movement of nozzle 304and 312 and respective material deposition rate. Processor 330 changesthe distance between the first 332 and second 336 pattern layers as afunction of the shape and wall thickness of the complex shaped 3D objectto be produced. Processor 330 also changes the amount of the secondmaterial 340 to be deposited by nozzle 312 in the varying space orvolume between the first 332 and second 336 pattern layers. Nozzle 304communicates with respective material supply mechanism 316 configured tosupply the first material to nozzle 304 and nozzle 312 communicates witha material supply mechanism 324 configured to supply to nozzle 312 thesecond material 340. The second material deposition rate is alsocontrolled by processor 330 and could be adjusted to provide asufficient amount of the second material to fill the varying spacebetween the first 332 and second 336 pattern layers.

In addition to controlling the first and second material depositionrate, processor 330 controls the relative displacement speed of nozzles304 and 312 and table 328. Table 328 is configured to receive and holdthe first type of material and the second type of material. Table 328could move in multiple (at least three) directions (for example X, Y, Z)as shown by arrows 342 to accommodate during material deposition forchanging size or dimensions of the manufactured complex shaped 3Dobject. Alternatively, nozzles 304 and 312 could be moved in multipledirections, for example the vertical (Z) and horizontal (X, Y)directions. In some examples table 328 could be heated to a higher thanthe environment temperature for faster initiation of curing or hardeningof the second material.

Nozzle 304 forms a first and second pattern layers 332 and 336 of thecasting form or mould of the complex shaped 3D object e.g., object 200or similar. The first material deposited or extruded by nozzle 304 couldbe a pseudo-plastic material in gel aggregate state such as the materialdisclosed in U.S. Pat. No. 9,216,543 and U.S. patent application Ser.Nos. 14/943,395 and 15/665,472 all to the same assignee. Thepseudo-plastic gel, is commercially available under name DIMENGEL® fromthe assignee of the present application, flows through the depositionnozzle 304 because of the agitation applied by mechanism 316. The gel'selasticity recovers immediately after leaving the nozzles, and the gelsolidifies or hardens to maintain or regain its shape and strength.After leaving the nozzle the material is no longer under stress and thenetwork recovers immediately, resulting in the gel re-solidificationImmediately after the gel solidification the gel is exposed to UV lightfor fixating the gel as fully polymerized to crosslinked. The solidifiedor hardened gel forms first 332 and second 336 pattern layers or walls332 and 336 of the casting form or mould for complex shaped 3D object.

DIMENGEL® however does not support easy patterns layers removal. Thepresent disclosure suggests a material facilitating easy patterns layersremoval. The novel pattern layers material composition based onhydrophilic monomers combined with hydrophilic or hydrophobiccrosslinks. This chemical structure allows the rapid swell of thepolymer but not full dissolution in the water. The outcome of the highstress, the hydrogel break into beads that can be easily collected intoa sieve, for example, by filtering the water through a sieve filter.

Rapid solidification or hardening of pattern layers or walls 332 and 336(also termed as layer pinning) takes less than 1 second and facilitatessecond material deposition by nozzle 312. Rapid solidification orhardening of pattern layers or walls 332 and 336 maybe furtheraccelerated by use of a photo-initiator pre-embedded within the gelformulation and ultraviolet (UV) radiation provided by a UV source. Thissecond material 340 is the casting material of the complex shaped 3Dobject to be fabricated or manufactured. The second material 340 couldbe selected from a large group of materials and large techniques forpolymerization including mixture of resin and hardener in differentratios, or external initiation including heat, light, microwave,electron beam or any source of external radiation. The outcome ofthermally curable polymer material can be initiated using catalyst orinitiator, catalytic pair, curable polymers of catalyst and roomtemperature accelerator. The polymers include combination of step growthpolymerization using monomers pairs, or chain-growth polymerization,polycondensation, or ring opening polymerization. The thermosettingpolymers include large types of polymers including: Epoxy resins,Vinylesters, Polyesters, Acrylates, Polyurethanes, Polyurea, Vulcanizedrubber, phenol-formaldehyde, Urea-formaldehyde, Melamine resin,Benzoxazines, Polyimides, Bismaleimides, Cyanate esters, polycyanurates,and Silicones (Referred to hereinafter as thermosetting polymers.) Insome examples, artificial stones compositions consisting of a mixture ofinorganic and organic components could be casted. The inorganiccomponents of artificial stones could be such as crashed marble orgranite, glass and carbon fibres or glass particles, metallic particlesof aluminium or alloys such as boron-nitride. The binder for the castingmaterial could also be inorganic, such as cement, gypsum and similar.

The second material is deposited in the space between pattern layers 332and 336 and forms together with the pattern layers or walls a strongreinforcement structure. When the curable polymer 340 is extruded fromnozzle 312 by apparatus 300 in layer form, the material layers solidifyupon being subject to mixing, heat or actinic radiation. Being inpermanent contact with pattern layers 332 and 336 the materialsolidifies and enhances the strength of the complex shaped 3D object.

In some examples, the solidification or hardening process of secondmaterial 340 could be enhanced and accelerated by a source of thermal(heat), microwave, IR radiation, electron beam or any source of externalradiation configured to harden (cure) the second type of material.

The first material could have physical properties different from thesecond material. The properties could include modulus of elasticity,transparency, appearance, material hardening radiation wavelength andother properties. In some examples, sources of material hardeningradiation 344 and 346, for example UV (ultraviolet) radiation could bearranged to irradiate the desired part of the complex shaped 3D objector pattern layers. Processor 330 is also configured to control operationof all types of sources of material hardening radiation.

FIG. 3B is another example of an apparatus suitable for manufacture of acomplex shaped 3D object. Apparatus 350 includes two material depositionnozzles 304 and 354 located at a variable distance or laterally shiftedwith respect to each other and configured to deposit a first materialand a nozzle 312 configured to deposit a second material. The twomaterial deposition nozzles 304 and 354 are configured to deposit afirst material to concurrently form a first 332 and second 336 patternlayers. Material deposition nozzles 304 and nozzle 312 could move in thevertical (Z) and horizontal (X, Y) directions independently of eachother, similar to what is disclosed in U.S. Pat. Nos. 9,011,136 and9,623,607 to the same assignee. The first 332 and second 336 patternlayers form a space (empty volume) with a cross section that variesalong the first 332 and second 336 pattern layers. Processor 330 isconfigured to receive the complex shaped 3D object data and convert itto movement of nozzle 304 and 354 and respective material depositionrate. Processor 330 changes the distance between nozzle 304 and 354 todeposit the first 332 and second 336 pattern layers as a function of theshape and wall thickness of the complex shaped 3D object to be produced.Processor 330 also changes the amount of the second material 340 to bedeposited by nozzle 312 in the varying space or volume between the first332 and second 336 pattern layers.

The distance or gap between the first 332 and second 336 pattern layerschanges also as a function of design. Nozzles 304 and 354 communicatewith respective material supply mechanisms 316 and 320 configured tosupply the first material to nozzles 304 and 354 and nozzle 312communicates with a material supply mechanism 324 configured to supplyto nozzle 312 the second material 340. A processor 330 is configured toreceive the complex shaped 3D object data and convert it to respectivematerial deposition rate. The second material deposition rate is alsocontrolled by computer 330 and could be adjusted to provide a sufficientamount of the second material to fill in the varying space or volumebetween the first 332 and second 336 pattern layers.

In addition to controlling the first and second material depositionrate, processor 330 controls the relative displacement speed of nozzles304, 354 and nozzle 312 and table 328. Table 328 is configured toreceive and hold the first type of material and the second type ofmaterial. Table 328 could move in three directions (for example X, Y, Z)as shown by arrows 342 to accommodate during material deposition forchanging size or dimensions of the manufactured complex shaped 3Dobject. Alternatively, nozzles 304 and 354 and nozzle 312 could be movedin the vertical (Z) and horizontal (X, Y) directions independently ofeach other. In some examples table 328 could be heated to a higher thanthe environment temperature to pattern faster initiation of curing orhardening of the second material.

Nozzles 304 and 354 deposit the first and second pattern elements layers332 and 336 of a complex shaped 3D object 300 (100 or 200). The firstmaterial deposited or extruded by nozzles 304 and 308 could be a waterbreakable material, heat radiation or a mechanical action, such asforce/pressure breakable material.

Use of breakable material for pattern elements layers 332 and 336facilitates easy patterns layers removal. For example, a pattern layersmaterial composition based on hydrophilic monomers combined withhydrophilic or hydrophobic cross linkers. This chemical structure allowsthe rapid swelling of the polymer but not fully dissolve in the water.As the outcome of high stress, the hydrogel break into beads that can beeasily collected into a sieve, for example, by filtering the waterthrough a sieve filter.

Typical first material or water breakable material composition includesacrylamide, methacrylamide, acrylate, acrylic acids and its salts,hydroxy(meth)acrylate, carboxy(meth)acrylate, acrylonitrile,carbohydrate monomers, methacrylate and polyfunctional acrylics.

Typical first material or water or heat radiation breakable materialcomposition could further include poly(ethylene glycol) (PEG), otherwiseknown as poly(oxyethylene) or poly(ethylene oxide) (PEO) at molecularweight (MW) range from 44 Dalton through oligomers at low molecularweight to high molecular weight polymers up to 300,000 Dalton. The PEGoligomers or polymers can be heterobifunctional, homobifunctional,monofunctional, PEG Dendrimers and Multi-arm PEGs and PEG Copolymers.The PEG based polymers display low melting temperature (Tm), at 60° C.,therefore it is easily break under exposure to mild heat. Similarmaterials can be of low melting temperature includes polycaprolactone(PCL), ethylene-vinyl acetate copolymers (EVA),Polyethylene-co-methacrylic acids, Polypropylene carbonate (PPP) orsimilar polymer displaying Tm at about 45-60 degree C.

In addition, non-reactive additives can be included, including water ororganic solvents. In addition to those solvents, short oligomers can beincluded to be used as plasticizers, reducing the melting temperatureand the polymer rigidity.

In some examples, other than thermosetting polymers materials could bedeposited between the pattern layers. Such materials could be differentwaxes, water resistant photopolymers, water-based mixtures with mineralbinders such as cement, gypsum and others.

In some examples, the solidification or hardening process of secondmaterial 340 could be enhanced and accelerated by a source of curingradiation configured to harden (cure) the first type of material and asource of radiation configured to harden (cure) the second type ofmaterial. The source of curing radiation configured to harden (cure) thesecond type of material could be a thermal, microwave or IR source ofradiation. The heating is enhancing not only the curing yield but alsoits speed, for faster and more efficient polymerization.

Apparatus 350 deposits simultaneously the first and second patternlayers 332 and 336. In some examples, there could be a delay betweendeposition of pattern layers 304 and 308 and the complex shaped 3Dobject casting material 340. Typically, casted complex shaped 3D objectmaterial layers 224 are deposited after several pattern layers 332 and336 are deposited and hardened. The delay could be defined by timerequired to deposit 3-30 pattern layers 332 and 336. By performing anumber of successive passes a desired number of hardened layers of thesecond material bounded by the first material could be deposited and a3D object could be produced.

In some examples, sources of material hardening radiation 344 and 346could be arranged to irradiate the desired part of the complex shaped 3Dobject or pattern layers. Processor 330 is also configured to controloperation of sources of material hardening radiation 344 and 346.Sources of material hardening radiation 344 and 346 could also includesources of the second material hardening radiation.

FIG. 4 is another example of an apparatus suitable for manufacture of acomplex shaped 3D objects. Apparatus of FIG. 4A simplifies manufactureof symmetrical 3D objects. Object 414 is a complex shaped symmetric 3Dobject similar to complex shaped 3D object of FIG. 1 . Pattern layers406 and 410 could form between them a space into which the secondmaterial forming object 414 is casted. Table 328 in addition to linearmovement is configured to provide a rotational movement as shown byarrow 420. Rotational movement of table 328 is supplemented by radialmovement of first and second material deposition nozzles illustrated bytheir material supply mechanisms 316, 320 and 324. Combination of table328 rotation and independent radial movement (arrows 416, 418 and 420 inFIG. 4B) of material deposition heads 316, 320 and 324, facilitatesfabrication or production of symmetrical articles 414 with variablegeometry, for example the diameter of the 3D object could vary, amountof casted material, or distance between boundary elements 406 and 410could vary. Additionally, table 328 could move in multiple directions toaccommodate for changing size of the complex shaped 3D object 414.Alternatively, nozzles 304 and 308 and nozzle 312 could be moved inmultiple directions (X, Y, Z) or at least in one direction.

Similar to the previously disclosed method, the second material is athermally curable polymer material, i.e., thermosetting polymers,deposited in the volume or space between pattern elements layers 406 and410 forms a strong pattern or self-patterning structure. When thethermally curable polymer 414 is extruded from nozzle 312 by apparatus400 in layer form, the thermally curable polymer material layerssolidify upon being subject to heat or infrared radiation. Being inpermanent contact with pattern layers 406 and 410 the thermally curablepolymer material solidifies and enhances the strength of the complexshaped 3D object.

According to an additional example the complicated shapes closest tosecond material 414 (or 340) side of pattern structure element 332 couldinclude a relief that will be copied to thermally curable polymer 414(or 340) of the casted material of the complex shaped 3D object.

In a further example apparatuses 300 and 400 could include more than onehead 324 with nozzle 312. Additional heads with nozzles 312-1 and 312-2could deposit material different from the material deposited by nozzle312. These materials could be different in appearance, colour andstructure to form on complex shaped 3D object side closest to patternlayers 410 a decorative pattern.

Pattern layers usually have to meet several conditions: maintain theprinted object integrity, to be easily removable of the 3D object andwhen removed they do not damage the surface of the 3D object. When avery large and or heavy complex shaped 3D object 500 (FIG. 5 ) has to bemanufactured, the pattern layers 506 and 510 could be further enhancedby additional (known in the art) supports 514, 516 and 520. Additionalsupport structures 514, 516 and 520 maintain the complex shaped 3Dobject integrity, and could be made of the same water or heat radiationbreakable material as pattern layers are made or a different material.Since support structures 514, 516 and 520 have no contact with complexshaped 3D object 500 and their removal will not leave any impressions orartefacts on the surface of complex shaped 3D object 500 and as suchthey could be made of other than water breakable materials.

FIG. 6 is a plan is a view of large size complex shaped 3D object.Complex shaped 3D object 600 includes an additional 3D object 604located in the inner cavity of complex shaped 3D object 600. Numerals606 and 610 mark respective pattern layers made from the first materialthat could be described above water or heat breakable materialfacilitating easy patterns layers removal. Numeral 602 marks the castingmaterial of complex shaped 3D object 600.

Use of the water or heat breakable material offers a large designfreedom. It allows for complex geometries to be produced by using apattern that “on command” disappear, leaving the complex geometry of thecasted material, without the need for designing complex mold.

In a further example, illustrated in FIG. 7 the material 702 from whichthe complex shaped 3D object 700 is formed is deposited in arbitrarilyselected locations of volume 704. Material 702 deposited in course ofobject 700 manufacture. A filling opening 708 could be provided in atleast one of pattern layers 712 and/or 716. Although complex shaped 3Dobject 700 is shown as a closed object, it could be a truncated objectwith free access to both of pattern layers 712 and/or 716.

Upon completion of pattern layers 712, 716 and material 702 deposited inarbitrarily selected locations 704 of volume enclosed between patternelements layers 712 and/or 716, pattern layers 712, 716 could be removedfrom the 3D printing machine and the space between them filled bymaterial 702 or a similar one. Such method releases the machine forprinting the next part and supports use of a variety of differentmaterials that could be sequentially introduced through filling opening708. The materials could be of different colour or possess differentmechanical properties. Objects of composite materials could also beproduced using this method. The hardening of such materials could beaccomplished off-line.

The method and apparatus have been described in detail and withreference to specific examples thereof, it will be apparent to one ofordinary skill in the art that various changes and modifications can bemade to the method and apparatus without departing from the spirit andscope thereof.

What is claimed is:
 1. A method comprising: employing a first polymericmaterial to deposit first and second pattern layers laterally shiftedfrom each other such that laterally shifted pattern layers form betweenthem an empty volume with a variable cross-section that varies alongwith the first and second pattern layers; casting in the empty volumebetween the first and second pattern layers a second polymeric materialto cast a complex-shaped 3D object identical in shape to the emptyvolume between the first and second pattern layers; applying radiationto cure the first and second polymeric materials; and wherein the firstpolymeric material is a water breakable material composition includingacrylamide, methacrylamide, acrylate, acrylic acids, and acrylic acidsalts, hydroxy(meth)acrylate, carboxy(meth)acrylate, acrylonitrile,carbohydrate monomers, methacrylate and polyfunctional acrylics.
 2. Themethod of claim 1, wherein the first material further includespoly(ethylene glycol) (PEG) at the molecular weight (MW) range from 44Dalton up to 300,000 Dalton.
 3. The method of claim 2, wherein the PEGcan be heterobifunctional, homobifunctional, monofunctional, PEGDendrimers and Multi-arm PEGs and PEG Copolymers.
 4. The method of claim1, wherein the first material is water soluble material.
 5. The methodof claim 1, wherein a chemical structure of the first material allowsrapid swell of the polymer but not full dissolution in the water.
 6. Themethod of claim 5, wherein the rapid swelling generates in the firstmaterial high stress that breaks the first material into beads.
 7. Themethod of claim 1, wherein the second polymeric material has inclusionsof additive materials therein.